
/*    This file is part of the managarm operating system.
 *   Copyright (C) 2007, 2008, 2009  Alexander van der Grinten
 *
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program.  If not, see <http://www.gnu.org/licenses/>. */

package org.managarm.jmanaintlib.runtime.system;

import java.io.InputStream;
import java.io.IOException;
import org.managarm.jmanaintlib.machine.VmError;

public class RtInStreamChannel extends RtChannel {
	private final InputStream inputStream;
	private int lastByte; // cached byte
	
	public RtInStreamChannel(InputStream input) {
		inputStream = input;
	}
	
	private byte readSingle() throws VmError {
		if(lastByte != -2) { // if there is cached data return it
			final int databyte = lastByte;
			lastByte = -2;
			return (byte)databyte;
		}
		
		try {
			return (byte)inputStream.read();
		} catch(IOException e) {
			throw new VmError("Error while reading from stream");
		}
	}
	
	@Override public void readBytes(byte[] buffer, int offset, int length)
			throws VmError{
		for(int i = offset; i < offset + length; i++)
			buffer[i] = readSingle();
	}
	
	@Override public boolean endOfChannel() throws VmError {
		try {
			if(lastByte == -2)
				lastByte = inputStream.read();
			if(lastByte == -1)
				return true;
			return false;
		} catch(IOException e) {
			throw new VmError("Error while reading from stream");
		}
	}
}
